When a SWAT team responds to a call such as Tuesday's stand-off, decisions on procedure depend on the events at hand.

"There's guidelines that every tactical team uses, but there's no manual, because every situation's different," said Oregon State Police SWAT tactical commander Tim Fox.

He was one of about 14 SWAT members, including three negotiators, who went to a dwelling near Harrison Boulevard and 25th Street on Tuesday morning in response to a call from an Oregon State University student who rents an apartment there. The student reported that his 29-year-old neighbor, who lives in an adjoining basement apartment, threatened him with a knife. The alleged knife-wielder then barricaded himself in his basement apartment.

Fox said the decision to call SWAT is up to the lead agency - in this case, the Corvallis Police Department - but Fox evaluates each call to make sure the team is really needed.

The first criterion, he said, is whether a crime has been committed. Fox also wants to know that the lead agency plans to take any suspects into custody.

From there, SWAT proceeds based on information from the lead agency. On Tuesday, Fox said, there was an indication that the suspect, Nathan Lenahan, had a gun safe in his room in addition to the knife he'd used to threaten the victim. Fox said that information raised flags.

"We know if he's willing to go that far, he's probably willing to go the extra distance," Fox said.

A negotiator using a shield as cover was able to speak with Lenahan through a broken window, but Lenahan seemed to be having mental health issues and was talking about the Antichrist.

Lt. Jeff Lanz of the Oregon State Police said Lenahan was "refusing to come out and basically stand down and cooperate."

Four hours after police first responded, Lenahan still refused to leave.

"We weren't making any headway with him, because of his mental status, I think," Fox said.

So when the opportunity presented itself, a SWAT member stunned Lenahan with a Taser from 6 to 8 feet away. Lenahan fell to the ground, enabling SWAT officers to enter the house and take him into custody.

The decision to use force against a suspect is based on the situation at that moment, considering "where we're at in negotiations, where I feel we're going to be," Fox said.

"We have a lot of tools at our disposal," Fox said, including Tasers and gas. "We have a lot of less-lethal options."

The safety of people in the surrounding area is a major factor in how to proceed. Tuesday's incident attracted a large crowd of onlookers.

"I don't think we've ever had that many people watching before," he said.